But police expect the death toll to climb and it will do so appreciably if the estimates about those missing in the CTV building are correct.

Fifteen CTV staff and a number of Japanese students from a foreign language school that operated in the building are believed to be among those in the rubble.

Canterbury police district commander Superintendent Dave Cliff gave the estimates of between 80 and more than 100 for those missing in the CTV building, soon after a colleague said that rescue work at the site had been halted by safety concerns. Inspector Dave Lawry said he was "100 percent sure" there were no survivors in the building.

"We're working on the assumption that everyone we haven't managed to contact was in the building, and that would number probably 15," he said.

"We haven't had anything confirmed, we haven't been given any names, we're just going off our own tally."

Mr Smith, business manager and director of Allied Press of Dunedin, which owns the Otago Daily Times, said he had travelled to Christchurch today to support staff.

"We're just having a staff get-together with those who have survived. That's the most important thing at the moment," he said.

"(They've) lost a lot of friends, a lot of colleagues, a lot of talent and a lot of life-long relationships...

"They're not happy. It's very sorrowful."

Many of the staff there were in the building when the quake struck and broke down when they told him what had happened. What staff had described to him was "like out of a horror movie", Mr Smith said.

"It's just too horrific to think that they got out and...people who were a few yards behind didn't. They didn't know which way to run."

Mr Smith's brother, Allied Press of Dunedin chairman and managing director Julian Smith, said the building had withstood the first quake well.

"So it seems strange that this whole building should fall down like that," he told NZPA.

"Our sympathy goes out to all staff - everybody in Christchurch, for that matter but particularly for the staff of CTV and their families."

Other CTV victims include Japanese students, police staff

Earlier today, Inspector Dave Lawry said he was "100 per cent" certain those trapped in the CTV building, including a non-sworn police staff member and a group of overseas students, were dead.

He felt particularly sorry for the family of what is believed to be a group of Japanese students who died inside.

"At a certain point I'm not going to risk my staff for people where I believe there is no chance of survivability."

Fires burned in the CTV building overnight and no signs of life have been detected there by cameras or listening devices.

Christchurch area commander Dave Cliff said the loss of a staff member in the building was painful.

It meant police could relate to the loss and desperation being suffered by family with loved ones still trapped, he said.

Nancy Wu, whose husband Paul Wu is among the missing in the CTV building, said news that search and rescue workers were putting efforts at the site on hold was "devastating".

"But hopefully they will return and not give up because people can still be alive for many hours. We are not giving up hope."

Hope is also fading for those trapped in the Pyne Gould Corporation building in Cambridge Terrace, though at least four people were pulled from the debris there today, the last a woman - who had been trapped for 26 hours - around 2.30pm.

There had been no communication with anyone trapped in the building for some hours since then.

"We are reaching that phase where hope is beginning to fade, but we are still there," Mr Cliff said about the PGC building.

Twenty two people are believed by police to have died in the collapse of ChristChurch Cathedral. Police dogs had been through the area of the 130-year-old city landmark and officers were confident there were no survivors there, Mr Cliff said.

One of the city's tallest buildings the Grand Chancellor Hotel in Cashel Street is teetering.

Reports said the hotel had slumped in one corner, prompting fears that should it collapse it could destroy surrounding buildings.

It has been a grim time in the central city, with medical staff in rescue teams having to amputate limbs to help free people trapped in rubble.

Mr Cliff said despite the lack of contact with people in the collapsed buildings, police were remaining optimistic.

"It is certainly possible that people could be in cavities in some of those sites, so we are not losing hope. The urban search and rescue teams are here for that purpose."

The Government this morning declared a national state of emergency following what Prime Minister John Key described as the "death and destruction on a dreadful scale" of the quake.

"My sense tomorrow is we will moving into looking at packages for businesses, employees and those who will be struggling to make ends meet.

"At the moment really the sole focus has been on rescue and recovery and getting back the core services as quickly as we can.

"But very quickly people are going to have to address the issue that they have outgoings, they don't have jobs to go to, businesses can't reopen and that is not something that is going to be resolved quickly."

Mr Key said as with September 4 quake, some sort of package was likely to be brought in. The length of time it was in place would have to be discussed.

About 80 percent of the city remains without water.

Power had been restored to over 60 percent of Christchurch but progress was slow, lines company Orion said this afternoon.

The company said parts of Lyttelton had power again but Christchurch's eastern suburbs were more problematic due to network and road damage.

About 300 Australian police officers are among a large international contingent helping with rescue efforts.

Police asked people desperate to find loved ones to go to the family liaison centre at Papanui police station to register their concerns, rather than going to work sites and damaged buildings.

The Queen and world leaders have sent messages of sympathy.

"I have been utterly shocked by the news of another earthquake in Christchurch. Please convey my deep sympathy to the families and friends of those who have been killed; my thoughts are with all those who have been affected by this dreadful event," the Queen said in a statement on her website.

United States President Barack Obama and wife Michelle have sent their condolences to the victims of quake-ravaged Christchurch.

"Our thoughts and prayers are with all those whose lives have been touched by this tragedy, especially as they search for their loved ones and work to recover from this disaster," he said in a statement.

To assist in the rescue and recovery efforts, the US would deploy a US Agency for International Development Disaster Assistance Response Team, including an urban search and rescue team, to help with the rescue and recovery effort.

UK Prime Minister David Cameron was one of a number of other world leaders to send their sympathies.